Why Grey's Anatomy's 300th Episode Will Have You Seeing Ghosts

When the long-running ABC hit celebrates its milestone 300th episode on Thursday, Nov. 9, you just might find yourself seeing ghosts of Seattle Grace surgical interns past. The special episode, written by season 14 showrunner Krista Vernoff, will act as a love letter to long-time fans of the show and the characters they've been forced to say goodbye over the years.

"Episode 300 is going down kind of like memory lane. We'll see some actors who come into the hospital after a horrific accident who remind us of Izzie and George and Cristina Yang," OG star James Pickens Jr. told E! News' Sibley Scoles at the show's big party in Los Angeles over the weekend. "And it's so cool how they do it. And they found three remarkable actors...When I came and I saw them, I said, 'Wow,' because they were such integral parts of the success of the show and such amazing talents in their own rights, so we miss them very much. So it will be nice for the audience to say, 'Oh wow, there they are.'"

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In the episode, which sees the doctors of Grey Sloan Memorial tending to the victims of a freak accident involving a roller coaster at the county fair, a trio of patients who look an awfully lot like Katherine Heigl, T.R. Knight and Sandra Oh will throw Meredith (Ellen Pompeo), Alex (Justin Chambers) and everyone else who knew the OG characters for quite a loop. But the homages to days of Grey's Anatomy past won't stop there.

"All I can say is, just keep your eyes wide open because there are a lot of little surprises in there for you," Debbie Allen, the episode's director, admitted. "There's a lot of little nuggets and throwbacks to the past. I call it our Hubble telescope episode, because the Hubble telescope lets you look back into the past and forward. And this show, it's all of that."

In particular, get ready for Grey Sloan's new intern class to come into focus with some behavior that's very, very reminiscent of Mer and Alex's early days in the hospital.

"This whole season has kind of been a love letter to the fans, people who've been there and paying attention since the beginning. Everything you've seen this season that's kind of like, if you check social media, people saying, 'Oh, that's kind of a hallmark to this, that's kind of a callback to that, throwback on this.' This episode is that in spades," Jason George added. "So everything you've ever loved about the show—people are going to be clutching their pearls, getting some feels. You're going to feel some kind of way about it."

For more from the cast and crew on what to expect from the big episode, including creator Shonda Rhimes' one-word description of the monumental episode, be sure to check out the video above. And for more on all things Grey's Anatomy in the lead up to the big 3-0-0, check back with E! News all week!